CVE-2019-19521

libc in OpenBSD 6.6 allows authentication bypass via the -schallenge username, as demonstrated by...

9.8 Critical

libc in OpenBSD 6.6 allows authentication bypass via the -schallenge username, as demonstrated by smtpd, ldapd, or radiusd. This is related to gen/auth_subr.c and gen/authenticate.c in libc (and login/login.c and xenocara/app/xenodm/greeter/verify.c).

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: High

Exploit likelihood

2.74%Up 1.1 points since Apr 14, 2021

What each source reports

NVD Score used 9.8

Record: CVE-2019-19521
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0: 7.5 HighAV:N/AC:L/Au:N/C:P/I:P/A:P
Weakness: CWE-287
Updated: 2026-11-02

CVE List No score

Record: CVE-2019-19521
Updated: 2026-11-02

EUVDEUVD-2019-9139 No score

Record: EUVD-2019-9139
Updated: 2026-11-03

GitHub AdvisoriesGHSA-gw7q-976q-g767 9.8

libc in OpenBSD 6.6 allows authentication bypass via the -schallenge username, as demonstrated by...

Record: GHSA-gw7q-976q-g767
CVSS 3.1: 9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-287
Updated: 2026-11-02

Affected products

openbsd

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2019-19521 is a critical vulnerability (CVSS 9.8) in Openbsd, published December 4, 2019. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.74%, the 86th percentile. No source names a fixed version.